1. Field of the Invention
This invention relates to a plasticizing assembly for use in an injection molding machine for processing synthetic materials, comprising a plasticizing cylinder at which a nozzle body is mounted and that is provided with a rotatable feed screw disposed in a cylindrical chamber with an inside diameter substantially corresponding to the diameter of the feed screw. The inside diameter of the nozzle body section is tapered to the inside diameter of a nozzle channel, taking as a starting point the rear end diameter of a transition section between the plasticizing cylinder and the nozzle body.
2. Description of the Prior Art
A plasticizing cylinder of this kind is, for example, known from German Patent 41 05 731. In general, and also in the case of the plasticizing cylinder mentioned before, it is unusual to use plasticizing cylinders with different inner diameters for different feed screw diameters. Since the diameter at the transition toward the nozzle body is formed in dependance on the diameter of the feed screw, to ensure a continuous surface area, especially in the transition section, it is necessary to assign to each respective plasticizing cylinder only one nozzle body. Therefore each time the plasticizing cylinder is changed, the nozzle body also has to be changed. This contributes considerably to increased costs, because every time a plasticizing cylinder has to be changed, a nozzle body also has to be placed at disposal. This is the case even if the outside diameter has remained unmodified, since, for example, the same type of heating collars are arranged on the surface of the respective plasticizing cylinder. Although the nozzle body would fit perfectly on the new plasticizing cylinder as to its connecting means, it is nevertheless necessary to exchange it together with the plasticizing cylinder.
From German Published Patent Application 21 21 270 it has been known for a long time to build the injection head of screw-type extruding machines by stringing together different discs. This is necessary to shape the extruded column before it leaves the injection head. The complicated shape of the inner injection head basically makes refrigeration more difficult, particularly for the temperatures applied in this case. Also the cleaning of this region is made more difficult. These are the two principal reasons for the suggestion to dismember the injection head into corresponding discs. Because the different material types applied require different conformations of the inner injection head, they are not destined to constitute a transition section between a plasticizing cylinder and a nozzle body.